The invention relates to a dynamic pressure bearing device, and more particularly to a dynamic pressure bearing device having a structure in which an opening is formed in each of both the end portions of a housing, a shaft is passed through the housing so as to form radial dynamic pressure bearings and thrust dynamic pressure bearings in the housing such that forces can be easily balanced with each other, and lubricant hardly leaks.
In a hard disk drive which is to be mounted in a personal computer or the like, in order to cope with high speed and high accuracy, a dynamic pressure bearing device using lubricant (working fluid) is used.
For example, a dynamic pressure bearing device is used in which, as shown in FIG. 5, a rotation shaft 31 is placed in a housing 30, V-like or herringbone-like radial dynamic pressure generating grooves 33 and 34 are formed in an inner peripheral face of the housing 30, a flange 32 is disposed on the rotation shaft 31, and thrust dynamic pressure generating grooves 35 and 36 are formed in a surface of the flange. In this case, a step 30c is formed in an upper portion of the housing 30, and a spacer 37 is placed, whereby chambers 38 and 39 are formed to prevent working fluid from leaking. In this way, dynamic pressure generating grooves are formed in the radial and thrust directions, so that a balance can be attained even for high speed rotation. In some cases, radial dynamic pressure generating grooves may be formed in the outer peripheral face of the rotation shaft 31.
Alternatively, as shown in FIG. 6, a rotation shaft 41 is placed in a housing 40, radial dynamic pressure generating grooves 43 and 44 are formed on the housing 40 or the rotation shaft 41, spacers 45 and 46 are respectively disposed in upper and lower portions of the rotation shaft 41,and a flange 42 on which thrust dynamic pressure generating grooves 47 and 48 are formed is disposed on the rotation shaft 41. Furthermore, when flow of the lubricant serving as a working fluid occurs, circulator holes 50 and 51 are disposed and chambers 52 and 53 are formed, so that the working fluid is prevented from leaking to the outside.
In the dynamic pressure bearing device of the structure shown in FIGS. 5 or 6 having an opening in each of the end portions, one opening 30a or 40a is adjacent to the thrust dynamic pressure bearing portion, and the other opening 30b or 40b is adjacent to the radial dynamic pressure bearing portion. In this structure, when forces in the radial and thrust dynamic pressure bearing portions fail to balance with each other, a flow of the lubricant occurs. Therefore, the structure in which the circulator holes 50 and 51 and the chambers 38 and 39 are formed (FIG. 5) or the chambers 52 and 53 are formed (FIG. 6) as described above is employed. When the circulator hole 50, the chamber 38 or 52, or the like is disposed, there arises a problem in that the working cost and the assembly cost are increased. Moreover, the number of parts is increased and the structure is complicated. Furthermore, there is another problem in that a balance is easily lost by a moment load.
The present invention addresses the problems discussed above. It is an object of the invention to provide a dynamic pressure bearing device having a structure in which forces in the radial and thrust directions can be easily balanced with each other, and lubricant hardly leaks.
In order to solve the problems, the dynamic pressure bearing device of the present invention provides a dynamic pressure bearing device which comprises: a housing having an opening in each end portion; a shaft passing through the openings; and a flange disposed on the shaft, and in which radial dynamic pressure generating grooves and thrust dynamic pressure generating grooves are formed between the housing and the shaft, and between an internal space of the housing and the flange to form a radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion, respectively, wherein radial dynamic pressure bearings are respectively formed in vicinities of the end openings of the housing, and thrust dynamic pressure bearings for supporting both faces are formed between the radial dynamic pressure bearings.
The present invention is further provides radial dynamic pressure bearings between which thrust dynamic pressure bearings are formed on both faces of a flange and an internal space of a housing are interposed wherein the radial dynamic pressure bearings are formed symmetrically with respect to the thrust dynamic pressure bearings.
The present invention of also provides a housing for forming the radial dynamic pressure bearings with interposing the thrust dynamic pressure bearings wherein the housing is split into housing portions, a fitting guiding portion is disposed in a vicinity of the thrust dynamic pressure bearings, and,the housing portions are fitted to each other.